Light-emitting diode (LED) arrays have shown great potential as a light source in liquid-crystal display (LCD) backlighting systems. When compared to other light sources such as incandescent or fluorescent light sources, LED arrays are desirable for their low-temperature performance, ease of heat-sinking, dimming range, small size, low power output, and relatively low cost.
Although it is generally advantageous to use an LED array as the light source for a LCD backlight, some design challenges remain. For example, one class of known LED-based backlights uses arrays of LEDs that emit white light. However, white LEDs do not currently provide as broad of a chromaticity range as demonstrated by known fluorescent backlights. Another class of known LED-based backlights uses a combination of colored LEDs, such as red, green and blue LEDs, to provide a wider chromaticity range. Such multi-colored LED arrays require complex controls to maintain the desired chromaticity range as individual LEDs age. Another problem is that the multi-colored LED arrays provide poor color uniformity across the backlight. Additionally, LEDs are mass-produced devices that can only be customized at a significant expense.
Other challenges become evident when LED-based LCD backlights are used in displays that may additionally be used in a special night mode, where certain wavelengths (notably red wavelengths) cannot be used without interfering with other equipment an operator is using. Backlighting systems have been created that have separate day and night vision-mode lighting systems, with the night vision-mode systems incorporating filters to filter out interfering wavelengths. However, such systems require separate hardware to accommodate the day and night mode systems, which increases the size, cost and complexity of the LCD backlight.
It is therefore an object of the invention to provide an LED-based LCD backlighting system that can be customized to provide light with a desired chromaticity range.
It is another object of the invention to provide an LCD backlight that provides light having good luminance uniformity.
A feature of the invention is an LED array emitting light that is not within the visible spectrum.
Another feature of the invention is a reactive element that emits light within the visible spectrum when light from the LED array is directed thereto.
An advantage of the invention is that mass-produced LEDs may be used to produce an LCD backlight with a customizable chromaticity.